Refraction and Diffraction/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby A man, Tim, is swimming in a pool. A robot, Moby, is standing near the pool. An animation shows Tim looking up through the surface of the water at Moby, who is holding a letter. An animation shows Moby hold up the letter. Tim reads from a typed letter. TIM: Dear Tim & Moby, I don’t understand the difference between refraction and diffraction. Can you explain it to me? From Nuria. Hey, good question. Refraction and diffraction are both important properties of waves. An animation shows a group of bent horizontal line segments traveling across the top of the screen. A wavy line is shown traveling across the bottom of the screen. On screen text reads: “refraction,” “diffraction,” and “waves.” TIM: Let's look at light for a minute. An animation shows a light bulb emitting light. On screen text reads: light. TIM: Light is a form of energy that zooms around as both waves and particles, or photons. An animation shows the screen split in half. A wavy line is traveling across the left side of the screen. On screen text reads: “wave” and “light.” A dotted line is traveling across the right side of the screen. On screen text reads: “particle” and “photons.” TIM: Normally light goes straight, minding its own business unless something gets in the way. An animation shows a group of bent line segments traveling diagonally across the screen. On screen text reads: light. TIM: But if it goes into a new material — like from air to water or glass — it bends. This bending is called refraction. The line segments travel into a large piece of glass and their path of travel bends. When they reach the other side of the glass, the path returns to its original path of travel. On screen text reads: refraction. MOBY: --Beep? TIM: Well, it happens because light changes speed when it travels between materials of different densities. On screen text reads: air (less dense) On screen text reads: glass (more dense) TIM: If you look at something in a pool of water, you can see refraction at work. An animation shows an arm being submerged in water. The portion of arm that is under water is not aligned with the portion above the water. TIM: Water is denser than air, so when light goes from air to water, it slows down. An animation shows the screen split in half. In the top section of the screen, text reads: air (less dense). In the bottom section of the screen, text reads: water (more dense). A wavy line is traveling through the top of the screen into the bottom of the screen. The portion of line in the bottom section of the screen is not aligned with the portion in the top section of the screen and moves at a fraction of the speed. TIM: This slowing causes a shift in the light’s direction. The underwater object looks a little distorted and funny. An animation shows an arm being submerged in water. The portion of arm that is under water is not aligned with the portion above the water. Above the water, text reads: air (less dense). In the water, text reads: water (more dense). TIM: The amount the wave bends is known as the angle of refraction. An image shows a piece of glass in the shape of a triangle. A red line is traveling through the glass. The section of line inside the glass is bent. A dotted line is drawn from the point where the red line enters the glass to a point beneath the section of the red line that is inside the glass. An arc connects the red line and the dotted line. The arc is labeled “theta subscript r.” TIM: Different colors of light have different angles of refraction. An animation shows a blue line traveling through the piece of triangular glass, positioned below the red line. A dotted line is drawn from the point where the blue line enters the glass to a point beneath the section of the blue line that is inside the glass. An arc connects the blue line and the dotted line. The arc is labeled “theta subscript r.” TIM: Rainbows happen when all the colors making up white light refract at different angles through water droplets. An animation shows the screen split in half. In the top half, three varying sized water droplets are shown. Entering each droplet is a beam of white light. The section of beam traveling inside the droplet changes from white to rainbow coloring and is bending. When the beam exits the droplet, it remains the color of a rainbow and bends again. On screen text reads: “refraction” and “rainbow.” In the bottom half of the screen, a grass field and a rainbow are shown. MOBY: --Beep? TIM: Well, diffraction is somewhat different. Diffraction is the bending and spreading of waves, usually around an obstacle. An animation shows the screen split into four sections. In one of the sections, vertical line segments are being funneled through a small opening in a vertical line. When the segments exit, they are in the shape of an arc, starting small where they are being funneled through and expanding as they enter the more open space. In another section of the screen, vertical line segments are colliding into a square figure that is half their height. When they pass over the square figure, the top half of the segments remain vertical but the bottom halves are in the shape of an arc. The arcs start small as the cross over the square, but then gain in size as they enter the open space. In another section of the screen, rippling waveforms are shown, as could be seen on the surface of water. One motion occurs at the center of the space, shown as a circle. From that circle, larger circles generate around that point, getting bigger and bigger and spreading outward before finally settling again. In the last section of the screen, vertical line segments are traveling through two small openings in a vertical line. When the segments exit the two openings, they are in the shape of an arc and overlap to form a pattern of interlocked arches. On screen text reads: diffraction. TIM: Just like refraction, diffraction can happen with any kind of wave — light, sound, radio . . . Three images are shown: a light bulb, a speaker, and a radio tower. MOBY: --Beep? An animation shows Moby waving his hand. TIM: Ah . . . no, waving hello doesn’t count. Moby frowns. TIM: One example of diffraction is when waves spread out from a single source. An animation shows a radio tower. Four concentric rings continuously emanate from the top of the tower. TIM: If I yell something to you across the room, a bunch of sound waves come out of my mouth. Like this. An animation shows a number of concentric rings traveling from Tim’s mouth. TIM: The sound waves don’t all go in a straight line — they spread out so you can hear what I’m saying if you’re standing pretty much anywhere in the room. Waves diffract when they hit obstacles, too. MOBY: --Beep? An animation shows a number of concentric rings traveling from Moby’s direction across Tim’s face. TIM: Well, say some waves hit a barrier with a small hole in it. The waves will pass through the hole and spread out on the other side. An animation shows vertical line segments traveling through a small opening in a vertical line. When the segments exit, they are in the shape of an arc. TIM: If there’s more than one hole, the waves overlap on the other side, making a predictable interference pattern. An animation shows vertical line segments traveling through two small openings in a vertical line. When the segments exit the two openings, they are in the shape of an arc and overlap to form an interlocking pattern. MOBY: --Beep. TIM: Well, actually, diffraction is really useful. Scientists use diffraction of x-rays to make images of very tiny objects, like DNA, and very distant ones, like stars. On screen text reads: x-ray diffraction images. An image shows an x-ray of a group of UpperWord DNA. An image shows a cloud-like figure amongst stars. It is labeled “galactic center.” MOBY: --Beep. An animation shows Moby waving hello. TIM: I thought I told you those waves don’t count. MOBY: --Beep. An animation shows Moby front flip into the pool. TIM: Oh . . . um, yeah, all right. O.K., those are real waves, all right. An animation shows water droplets falling off of Tim’s head. Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts